Suitable membranes for blood‐contacting medical applications need to be resistant in confrontation with blood proteins and cells, while possessing high blood compatibility and permeability at the same time. Herein, an overview of the recent advances and strategies that have been used to enhance the hemocompatibility of polymeric membranes is provided. The review focuses on two modification strategies: (i) physical modifications and (ii) chemical modifications. It also highlights the current progress in the design of hemocompatible‐functionalized membranes for biomedical applications. Subsequently, the commonly applied biocompatibility tests are also discussed and finally the future perspectives of the application of polymeric membranes in the biomedical field are presented.
One major challenge of biomaterial engineering is to mimic the mechanical properties of anisotropic, multifunctional natural soft tissues. Existing solutions toward controlled anisotropy include the use of oriented reinforcing fillers, with complicated interface issues, or UV‐curing processing through patterned masks, that makes use of harmful photosensitive molecules. Here, a versatile process to manufacture biocompatible silicone elastomer membranes by light degradation of the platinum catalyst prior to thermal cross‐linking is presented. The spatial control of network density is demonstrated by experimental and theoretical characterizations of the mechanical responses of patterned cross‐linked membranes, with a view to mimic advanced implantable materials.
The introduction of nanodiamond particles (NDs) in silane‐crosslinked polyethylene is found to lead to a notable and systematic deformation of the polymer unit cell. X‐ray diffraction evidence of the existence of a modified crystalline structure in the bulk of the polymer due to the presence of NDs is reported here for the first time. The covalent bonding between NDs and the surrounding macromolecular chains may support that the excessive local stress field ultimately distorts the polymer conformation, yielding a new distorted but still crystalline interface. Supporting data from solid‐state NMR experiments confirm the existence of a modified crystalline interface of about 1–2 nm in all the nanocomposite materials.
A new facile approach for the fabrication of polymer‐Ag honeycomb film is reported. A polymer‐Ag+ honeycomb thin film is obtained by casting a CHCl3 solution of a functional graft copolymer on aqueous silver nitrate solution, leading to metal complexation induced phase separation at the air/water interface. The film is reduced by UV irradiation to give a polymer‐Ag honeycomb film with regular morphology. Pyrolysis of the film gives a translucent Ag honeycomb film.
A gas‐permeable cellulose template for microimprint lithography has been synthesized and characterized for the reduction of template damage and gas trapping caused by solvents and oxygen generated from cross‐linked materials. The 5 μm line‐pattern failure of the microimprinted UV cross‐linked liquid materials with 4.7 wt% acetone as a volatile solvent is solved by using the gas‐permeable cellulose template because of its increased oxygen permeability. The gas‐permeable cellulose template also allows the use of volatile solvents with high coating property and solubility into the microimprinted materials instead of the compounds and plastic resins conventionally used in mold injection.
Flexible polymers such as poly dimethyl siloxane (PDMS) can be patterned at the micro‐ and nanoscale by casting, for a variety of applications. This replication‐based fabrication process is relatively cheap and fast, yet injection molding offers an even faster and cheaper alternative to PDMS casting, provided thermoplastic polymers with similar mechanical properties can be used. In this paper, a thermoplastic polyurethane is evaluated for its patterning ability with an aim to forming the type of flexible structures used to measure and modulate the contractile forces of cells in tissue engineering experiments. The successful replication of grating structures is demonstrated with feature sizes as low as 100 nm and an analysis of certain processing conditions that facilitate and enhance the accuracy of this replication is presented. The results are benchmarked against an optical storage media grade polycarbonate.
The previously introduced process for enzyme‐mediated in situ synthesis and deposition of eumelanin is investigated with covalent immobilization of the tyrosinase. It results in a monolayer structure of non‐coalesced melanin particles, with a film thickness of 5–8 nm. The reaction is self‐terminating due to overlay of the enzymes with particles. The melanin particles are rodlike with lengths down to 6 nm. Isolated melanin structures of such small size have not been observed before and might be a kind of protoparticle in the supramolecular buildup of melanin oligomers. Utilization of melanin particles with such small size can enable nanotechnological applications in the areas of bioelectronics and biosensors.
The effect of varying electrospinning parameters is reported for the production of collagen nanofibers from acetic acid with controlled fiber diameter, orientation, and mechanical properties. Nanofibers with a range of diameters of 175–400 nm are obtained by varying either the voltage or the flow rate. An increase in nanofiber alignment is observed by increasing injection flow rate. Mechanical testing of these fibers reveals that the elasticity modulus can be tuned in the range of 2.7–4.1 MPa by the selection of the crosslinking method. Fourier transform infrared spectroscopy reveals that the secondary structure of collagen is preserved after electrospinning and crosslinking. Lastly, in vitro testing reveals that a high number of fibroblasts attach to the collagen matrices indicating, that they are suitable for mammalian cell culture.
A self‐cleaning membrane that periodically rids itself of attached cells to maintain glucose diffusion could extend the lifetime of implanted glucose biosensors. Herein, we evaluate the functionality of thermoresponsive double network (DN) hydrogel membranes based on poly(N‐isopropylacrylamide) (PNIPAAm) and an electrostatic co‐monomer, 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS). DN hydrogels are comprised of a tightly crosslinked, ionized first network [P(NIPAAm‐co‐AMPS)] containing variable levels of AMPS (100:0–25:75 wt% ratio of NIPAAm:AMPS) and a loosely crosslinked, interpenetrating second network [PNIPAAm]. To meet the specific requirements of a subcutaneously implanted glucose biosensor, the volume phase transition temperature is tuned and essential properties, such as glucose diffusion kinetics, thermosensitivity, and cytocompatibility are evaluated. In addition, the self‐cleaning functionality is demonstrated through thermally driven cell detachment from the membranes in vitro.
The mechanical properties and microstructure of injection molded isotactic polypropylene parts with high orientation before and after annealing are analyzed. The mechanical properties of the annealed samples are improved effectively. Through thorough analysis of various structural characterizations, a microstructural model based on the fact that the total length of long period kept constant to analyze the variation of mechanical properties is proposed. It is suggested that the increase of overall crystallinity, the recombination of crystalline phase, and the increase of amorphous phase, respectively, are beneficial for the improvements of the strength, stiffness, and toughness of annealed samples.
We report a novel method for oil/water separation using stainless steel meshes functionalized with amphiphilic copolymer, poly(methacrylic acid‐co‐ethylhexylmethacrylate) (PMAA‐co‐EHMA), brushes. Because the PMAA‐co‐EHMA brush‐covered surfaces show a large contact angle hysteresis at the oil/water contact line, the meshes can be programmed to act as either water‐selective or oil‐selective filters simply by pre‐wetting the mesh with one of these liquids. These programmable meshes can separate oil/water mixtures to high filtrate purities (more than 99 % mol/mol) in both oil‐selective and water‐selective modes.
A conjugated polymer, poly(9,9‐bis(6‐bromohexyl)‐9H‐fluorene‐alt‐1,4‐phenylene), is synthesized, converted to nanoparticles via a nanoprecipitation process, and utilized to fabricate thin films including conjugated polymer nanoparticles. The nanoparticles with surface bromides can be conjugated with an amine‐functionalized dendrimer via a nucleophilic coupling reaction. Thus, when microliter solutions of the particulates are dragged at a constant velocity on substrates alternately in a layer‐by‐layer manner, thin films composed of the nanoparticles and dendrimers can be successfully built up on the substrates. Our results suggest a methodology to control the deposition of thin films bearing conjugated polymer nanoparticles while minimizing processing time and decreasing material consumption.
This article deals with the amine blush phenomenon in epoxy coatings. Amine blush is due to amine carbonation and weakens the visual aspect of room temperature epoxy coatings. This paper describes a way to avoid the carbonation by preparing aminotelechelic prepolymers is described. For the first time, the amine‐adduct impact over amine carbonation, as well as the amine decarbonation with temperature, has been investigated by infrared spectroscopy. Moreover, a range of epoxy materials displaying various Tg are synthesized from amine‐adducts and compared to polyurethane references generally used for transparent coating applications. Mechanical and thermal properties are also investigated.
We herein report on an iontronic device to drive and control Aβ1‐40 and Aβ1‐42 fibril formation. This system allows kinetic control of Aβ aggregation by regulation of H+ flows. The formed aggregates show both nanometer‐sized fibril structure and microscopic growth, thus mimicking senile plaques, at the H+‐outlet. Mechanistically we observed initial accumulation of Aβ1‐40 likely driven by electrophoretic migration which preceded nucleation of amyloid structures in the accumulated peptide cluster.
Hydrophobic and super‐hydrophobic materials have many important applications, but most of the artificially hydrophobic and super‐hydrophobic surfaces suffer from poor durability. Herein, a facile method is reported to fabricate robust hydrophobic and super‐hydrophobic polymer films through backfilling the silica colloidal crystal templates with the mixture of fluoropolymer, thermoset hydroxyl acrylate resins, and curing agent. After removal of the template, 3D ordered porous structures are obtained. The obtained polymer films have not only excellent hydrophobic or super‐hydrophobic properties but also good stability against temperatures, acids, and alkalis. Dual ordered porous structure can obviously enhance the hydrophobicity of polymer films compared to unitary one.
Thermal induced solid phase polymer reactions between bisphenol‐A‐based polycarbonate (PC) and polyvinylamine (PVAm) are used to form permanent composite material. The PC–PVAm interface is characterized by infrared (IR) spectroscopy. IR spectra of synthesized reference substances which can be expected after PC–PVAm reaction are recorded and used to identify amidation product structures within the PC–PVAm interphase. Curve fit analysis is performed to isolated sub‐bands. The spectral position of the carbonyl absorption band is a suitable marker for the identification of different amidation products. While the formation of urethane and cyclic Allophanate points to the formation of a co‐polymer cyclic Urea indicates a PC chain scission without binding between both polymer materials.
In this study, polyamide 6/polystyrene in situ microfibrillar blends are prepared via anionic polymerization of ε‐caprolactam in a twin screw extruder. Scanning electron microscope analysis reveals that microfibrillated PA6 dispersed phase, which is continuous and preferentially oriented parallel to the extrusion direction, is in situ formed within polystyrene (PS) matrix during reactive extrusion at the content PS equal to 30 and 40 wt%. Mechanical properties analysis shows that the yield strength and elongation at break of PA6/PS (70/30 and 60/40) microfibrillar blends are remarkably increased with respect to those of pure PS. Also, the in situ fibrillation mechanisms are investigated by the analysis of morphological evolution. This work demonstrates a facile and efficient route to fabricate the microfibrillar blends with relatively high contents of polymer microfibrils.
Flexible sensors capable of detecting large strain are very useful for health monitoring and sport applications. Here a strain sensor is prepared by applying a thin layer of conducting polymer, polypyrrole (PPy), onto the fiber surface of an elastic fibrous membrane, electrospun polydimethylsiloxane (PDMS). The sensor shows a normal monotonic resistance response to strain in the range of 0–50%, but the response becomes “on‐off switching” mode when the strain is between 100 and 200%. Both response modes are reversible and can work repeatedly for many cycles. This unique sensing behavior is attributed to overstretching of the polypyrrole coating, unique fibrous structure, and elasticity of PDMS fibers. It may be useful for monitoring the states where motions are only allowed in a particular range such as joint rehabilitation.
Dopamine is a molecule that facilitates biomineralization, and it is used to prepare electropolymerization‐induced polydopamine (PDA). For the first time, dopamine is used for template‐free electrochemical polymerization to form biocompatible polypyrrole (PPy) nanofiber coatings on bone implants. Dopamine monomers are electropolymerized to PDA chains affixed to biomedical titanium after the nanomicelles are tuned to self‐assemble by triggering the potential, resulting in nanofiber formation. Dopamine serves as a dopant to induce the formation of conductive PPy nanofibers and as a promoter to accelerate biomineralization, cell proliferation, and adhesion.
The fabrication of asymmetric polymer membranes via vapor phase deposition is demonstrated. In this solventless process, the dense layer is deposited first and then the porous layer is subsequently deposited onto the dense layer. A variety of functional polymer membranes can be produced by varying the precursor molecules. The functionality of the dense and porous layers can be independently tailored to be either hydrophobic or hydrophilic, resulting in membranes that are fully hydrophilic, fully hydrophobic, or asymmetric in both structure and chemical functionality. The thickness of both the porous and dense layers can be separately tuned by controlling the deposition time.
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